Final Report: Shoddy Maintenance Blamed for King Air Aileron Problems

Hawker Beechcraft King Air C90A, Chickasha, Okla., April 11, 2011–The National Transportation Safety Board found that the mechanic’s improper installation of the aileron was the cause of its partial detachment from the King Air during flight. While on a downwind leg for landing at Chickasha Municipal Airport at the end of an instructional flight, a pilot-passenger in the cabin alerted the certified flight instructor that the right aileron had partially detached. The CFI took control of the airplane and landed it safely. Ten days before the incident the turboprop twin had undergone a phase inspection during which the aileron was removed to repair some light surface corrosion. The King Air had flown 5.3 hours since its reinstallation. Post-incident inspection revealed two of the three hinges on the aileron had become disconnected. The mechanic determined that the screws that attached the aileron to the hinge points were seated in the aileron skin but did not screw into the corresponding nut plates on the hinge points.

Hawker Beechcraft King Air E90, Des Moines, Iowa, Feb. 15, 2011–The failure of maintenance personnel to install the right aileron properly led to its loss during flight and subsequent damage to the aircraft, according to the NTSB. The turboprop twin had just undergone maintenance, which included an 800-hour inspection of the ailerons, and the pilot had performed a preflight inspection before taking the airplane on a test flight. In the course of a 180-degree turn to Des Moines International Airport, the pilot noticed the autopilot “jerked, stabilized and jerked again” during the turn to level off. The pilot then noticed the right aileron was missing. After an uneventful landing, examination revealed the outboard aileron hinge bracket had separated from the aft spar. The King Air 90 Series maintenance manual details the procedure for reinstalling the ailerons and cautions technicians to “Pull on the aileron straight away from the wing. If any movement is detected, carefully check the bolt installation.” In 2003, Raytheon Aircraft issued a bulletin alerting operators that during reinstallation of the ailerons, screws can miss the nut plates on the aileron hinge points, a condition that can go unnoticed.